Digital lighting technologies, i.e. illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. Some of the fixtures embodying these sources feature a lighting unit, including one or more LEDs capable of producing different colors, e.g. red, green, and blue, as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects.
Many lighting fixtures have been designed that implement LEDs to reap one or more of the advantages and benefits of LEDs. For example, some outdoor LED street lighting fixtures have been designed that enclose a plurality of LEDs in a shoe-box type housing, with the LEDs being in a generally horizontally planar configuration and generally aimed toward a desired illumination area. While such lighting fixtures may provide a high light output efficiency, they also produce a large amount of perceived glare to a pedestrian who may be traveling (e.g. in a car, walking, riding a bike) in the proximity of the illumination area. The glare may be non-aesthetically pleasing, discomforting, and/or even dangerous to a pedestrian.
Some LED street lighting fixtures have been designed that attempt to remedy glare from LEDs by aiming all of the LEDs away from the desired illumination area and redirecting light output from the LEDs toward the desired illumination area. The redirection may occur through, for example, use of a redirecting optical lens affixed over and immediately adjacent a single LED and/or one or more redirecting reflectors. While such lighting fixtures may help lessen the amount of glare, they may not lessen the glare sufficiently and/or may also diminish the light output efficiency of the lighting fixture through one or more light output reflections. Moreover, such lighting fixtures may require reflectors and/or optical lenses therein to be specifically designed to achieve a desired light output, thereby requiring a distinct reflector and/or optical lens for each distinct light output.
Thus, there is a need in the art for a low-glare LED-based lighting unit having a vertically extending array of individually aimed LEDs and at least one translucent inner lens provided adjacent a plurality of the LEDs and intersecting the LED light output axis of a plurality of the LEDs, thereby reducing perceived glare emitted from the LED-based lighting unit.